1. Technical Field
The embodiments described herein generally relate to methods and devices. More particularly, the embodiments herein relate to a positioning of fiber optic devices in predetermined directions.
2. Description of the Related Art
Fiber-optic communications are well known as methods of transmitting information from one place to another by sending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information. The positioning of the optical fiber output (i.e., the source of the pulses of light) is among the most common techniques in the fields utilizing the fiber optics. The static displacement of fiber optic output having high resolution can be accomplished utilizing numerous X, Y, Z types of positioners: manual or motorized. However, it is to be noted that these positioners are very cumbersome and have various issues with regard to fiber optic displacement. For example, linear micro-motor positioners have problems moving the fiber output long distances with high speed. Additionally, modem optical communication positioners designed for near-horizontal propagation of carrier laser beams suffer from degradation of performance due to atmospheric turbulences. In particular, the degradation of the carrier beam is a result of fast fluctuating deviations of the beam from the “ideal line” connecting the laser transmitter and photo-receiver.
Several solutions have been proposed to compensate for the above-mentioned fluctuating deviations using the fast the movement of fiber optic output emitted by the transmitter and/or the movement of the distal end of the fiber optic output emitted by the receiver via placement of a remote photo-detector located adjacent to the proximal end of the fiber optic emitted by the receiver. Devices for the fast displacement of fiber optic output are used in such systems including but not limited to: micro-bar code scanners, scanning optical microscopes, flexible endoscopes, and micro-machining vision devices. All of them use the resonant amplification of the fiber distal end displacement by means of exciting the cantilevered fiber forcing the fiber to vibrate at certain resonance frequencies.
In U.S. Pat. No. 6,845,190 to Smithwick et al, the features of a standard PID (proportional integral-derivative) control is described allowing to have different resonance scanning modes.
In U.S. Pat. No. 6,515,274 to Moskovits et al, the resonance excitation of very thin and short fiber tip, aiming to obtain a high Q-factor (up to 9000) is described. The fiber diameter used ranges from about 20 to 100 mkm. The length of the fiber tip is 0.1 mm to 9 mm and the scanning distance is about 1 mkm. Further, obtaining of very thin fiber tips up to 20 mkm diameter is also described. Calculations are presented for the influence of fiber tip dimensions (length L, diameter d) on Q-factor and resonance frequency.
In U.S. Pat. No. 6,091,067 to Drobot et al., a one-dimensional fiber optic scanner is described based on the fiber optic being placed between two sheets of piezoelectric material to provide the bending bimorph structure. However, there is no data about embodiments and characteristics of the deviation amplitude of distal end of fiber as well as no data about the frequency bandwidth and resonant behavior. Moreover, the is not suitable for two-dimensional steering of the fiber optic distal end.
A two-dimensional laser beam steering device is described in U.S. Pat. No. 5,295,014 to Toda, which is based on polyvinylidene-fluoride (PVDF) elements. The laser beam scanning is accomplished by means of mirrors connected to bimorph PVDF elements having different configurations. An electrical signal containing two frequency harmonics may induce x and y resonances at separated frequencies, thereby providing Lissajous patterns. However, it is problematic to consider this device for use in resonance-free fiber optic steering in wide frequency ranges, for instance exceeding 1 kHz, due to small stiffness of thin-film polymer-based piezoelectric material since the considerable deviations take place only at resonance conditions.
In U.S. Pat. No. 4,841,148 to Lyding, a piezoelectric tube scanner (device of Lyding) for scanning microscope is described. The tube is described as preferably being up to 6″ long (hence bulky and heavy) to provide the scanning up a range of 100 mkm.
A three-dimensional scanner for a scanning probe microscope is described in U.S. Pat. No. 5,173,605 to Hayes et al. In particular, the X, Y, Z scanning tube is comprised of two telescopic tubes with quadrant arrangement of electrodes on tubes. For large displacement, four telescopic tubes can be used. Further, it is claimed that displacement up to 200 mkm is possible for a 1 inch long system and multiple electrode patterns inside and outside of cylinders. Further, it was stated that described device should have better resonance performance, than previously patented devices, however, there is no data about actual scanning ranges and resonance behavior discussed.
In U.S. Pat. No. 5,170,277 to Bard et al, a piezoelectric beam deflector for compact bar code reader is described utilizing the cantilever mounted piezoelectric bimorph elements with mirrors or masks or photodiodes at the end of bimorphs. A resonance mode is considered, yet nowhere is data presented about other experimental embodiments.
In U.S. Pat. No. 6,999,221 to Sarkisov et al., PVDF bimorph actuators driven via light are described. However, this device can not be used for high frequency bandwidth due to three basic restrictions: 1) Very small stiffness of PVDF films to provide high enough distal end displacement, so the resonance frequency could be 2-3 orders less than ceramic or crystal materials; 2) The passive damping of bending actuators require the installation of damping material, which will block the controlling light; and 3) In most fiber optic base systems, there is not enough space to introduce additional elements such as, for example LEDs, lenses, and wires.
In U.S. Pat. No. 6,748,177 to Upton, a fiber optic positioner having multiple degrees of freedom is described, using a plurality of bimorph actuators connected end-to-end and forming an open square. Patterned electrodes on each actuator allow end user to control the structure of the actuators assembly and to accomplish up to 5 degrees of freedom (e.g., X, Y, Z, tip, tilt). The positioner is assumed to be used in free-space optical communication transceivers. However, the device is slow and is considered to compensate the disturbances of the laser beam propagation direction at low-frequency vibrations of mounts, building sway, etc. Additionally, the device has unwieldy and fragile structure.
Therefore, it has been determined that there are no compact lightweight devices for two-dimensional positioning or steering fiber optics in kHz frequency bandwidth having a displacement of distances of roughly 100 microns or more.